


in your childish, tender love

by yoonminoml (fanficloverme96)



Category: IDOLiSH7 (Video Game)
Genre: But nothing extreme, Fluff and Smut, Infantilism, M/M, Sibling Incest, Tender Sex
Language: English
Status: Completed
Published: 2020-07-25
Updated: 2020-07-25
Packaged: 2021-03-05 19:35:04
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 7,409
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25510684
Author URL: https://archiveofourown.org/users/fanficloverme96/pseuds/yoonminoml
Summary: Tenn continues to cry, whimpering against him like a helpless child as he grips onto his shirt. He looks small like this - it stirs an urge from within Riku to protect him. To keep him by his side and soothe his worries away before tucking him into bed and sing him to sleep.Riku doesn’t know when it first started.He barely remembers the first time he witnessed it - the regression.
Relationships: Kujou Ten/Nanase Riku
Comments: 6
Kudos: 41





	in your childish, tender love

**Author's Note:**

> Please heed the tags! Though it's nothing extreme, this fic has infantilism kink in it, and it will affect how Tenn behaves during sex. So if you're uncomfortable, please feel free to click away.

Ryuu had been the one who greeted him at the door.

“Riku-kun, thanks for agreeing to do this,” he says, his smile rueful, “I know it’s a short notice -,”

Riku shakes his head. “I don’t have anything scheduled this weekend so the timing is fine, Tsunashi-san! I’m happy you told me about it. May I come in?”

“Ah, of course!’

Gaku is crouching beside his small hand luggage when Riku steps into the living room of Ryuu’s apartment, fiddling with the lock. He lifts his head when he hears footsteps, his handsome face morphing into relief when he sees Riku. 

“Hey, Nanase. You got here alright.”

“Mmph. Are you and Tsunashi-san leaving soon?”

“Our plane for Okinawa leaves in two hours, so we should be heading to the airport soon,” Gaku explains, “Anesagi-san said she’ll be here in five so Ryuu and I were about to go to the lobby anyway. Glad you arrived in time so we could at least see each other before we leave.”

Ryuu lets out a sigh. “Tenn’s been resting in his room since yesterday after we got back from the doctor, but we don’t want to leave him alone in his state and he refused to go to the hospital. So we figured -,” He trails off, looking at Riku apologetically. 

Riku holds up his hands. “Don’t worry about it! I’m happy to help. Like I said, I don’t have anything scheduled either, so it works out.”

He sees them off at the door a while later, promising Gaku to call him if anything goes awry. With a wave of his hand, he watches them disappear into the elevator before he steps back inside and closes the door.

Riku glances towards the stairs. 

He doesn’t hear anything, so Tenn’s probably not awake. Still, he should check up on him. Gaku and Ryuu had given him a meaningful look before they left, and Riku knew what that look meant.

If his hunch is right -

He stands in front of Tenn’s room before his knuckles make contact with the wooden surface of the door in a single knock. Then, another one. When no one responds, he twists the doorknob and finds the door unlocked. Taking a deep breath, he pushes the door open and peeks inside. 

“Tenn-nii?” Riku calls out, standing by the doorway, “It’s me, Riku.”

The bundle of blankets moves, and Riku watches as a figure emerges from it, sitting up on the mattress like clockwork. He first catches sight of messy tufts of hair, before he sees the person’s flushed skin, and then his eyes meet that person’s.

And then he hears a strangled sob.

“R-Riku…?” Tenn squeaks out, “R-Riku...Riku’s here?”

Riku’s heart softens immediately at the sound of Tenn’s voice. He steps inside the room, smiling at his brother. “That’s right, Tenn-nii. I’m here.” 

He stops at the foot of the bed, opening his arms. “Won’t Tenn-nii give Riku a hug?”

There is a beat of silence.

Tenn throws his blankets to the side and practically launches himself towards Riku, his arms wrapping around Riku’s waist as Tenn buries his face against Riku’s chest. A wailing sob rips through the air a second later as tears begin to dampen the front of Riku’s shirt.

“Riku…” Tenn sobs, his voice dropping into a whine, “Riku…! Everything hurts and is fuzzy. Tenn-nii don’t feel good... “

Riku holds Tenn close, kissing the top of his hair. “That’s because you have a fever, sweetheart,” he soothes, “There, there. Don’t cry. Riku’s here, okay?”

Tenn continues to cry, whimpering against him like a helpless child as he grips onto his shirt. He looks small like this - it stirs an urge from within Riku to protect him. To keep him by his side and soothe his worries away before tucking him into bed and sing him to sleep.

Tenn is like a helpless child in this state...because that is the headspace he had slipped into. Emotionally and mentally, Tenn has reduced himself to a much younger state of mind to cope with the stress and anxiety.

Riku doesn’t know when it first started.

He barely remembers the first time he witnessed it - the regression. He vaguely knows it had been a particularly rough time for Tenn. He had shut himself in and wasn’t responding to texts and calls, even those of his teammates. Was it then? The time where TRIGGER first fell from grace at the hands of Tsukumo Ryo. When things went south for a while before TRIGGER found a foothold to stand on again.

Riku doesn’t remember the details, his fingers failing to grasp the edges of that particular memory, despite how fairly recent it is. Perhaps it’s his unconscious way of protecting Tenn’s secret. Protecting the one thing Tenn trusts him with him - that vulnerable part of him that he slips into when stress and anxiety threaten to overwhelm him. Tenn trusts Riku to allow him to witness him crawl into his safespace - a privilege he had only extended to Ryuu and Gaku before.

Riku supposes it’s also because Tenn was never spoiled or pampered as a child. It wasn’t because his parents didn’t want to. It’s because Riku had always been the priority - a fact that Tenn willingly accepted and embraced perhaps until today. He never complained when he got sick, because Riku always had it worse. He never whined when Riku received more gifts for special occasions because he knew that those gifts were to make up for the fact that Riku could rarely go out and play like Tenn could. Tenn never got angry when in their exhaustion, their parents forgot Tenn’s also their child and would go for days forgetting he’s there, because he conceded that Riku deserved and needed all their attention to live for another day.

But just because he never complained, whined, or got angry, Riku knew that it didn’t mean his heart wasn’t slowly hurting from all the sacrifices he made, even if those sacrifices were made willingly. Tenn’s only human, and humans hurt all the same.

And it’s perhaps that the same pain that personified itself into Tenn’s current child-like personality - as a way to demand back the attention he gave up as a child, even if Tenn himself isn’t fully aware of it. 

“Gaku and Ryuu left Tenn-nii alone,” Tenn whines again, wiping away his own tears with a huff, “They don’t care about Tenn-nii.”

“You know that’s not true,” Riku says with a fond chuckle, rubbing Tenn’s back, “If they didn’t care, they wouldn’t have called me over to stay with you, would they?”

“Still…”

“My poor baby,” Riku croons, “You must feel really icky right now, don’t you? This is why you’re so upset.”

He lets go of Tenn to examine his face. His cheeks are rosy red and his skin feels a little clammy to the touch. When Riku presses a hand against Tenn’s forehead, he frowns a little when he finds the skin underneath his hand feels rather hot. 

“Riku’s here so I’ll take care of you now, okay, Tenn-nii?”

Tenn looks at him with adorably wide eyes. “Riku won’t leave Tenn-nii?”

“Of course not! Riku will stay with Tenn-nii until Tenn-nii gets better, okay?”

Tenn pouts. “Tenn-nii wants Riku to stay longer than that!”

“Mmph! Riku and Tenn-nii will have a sleepover while Tsunashi-san and Yaotome-san are away. Once you’re better, we’ll watch movies and play games and eat lots of delicious food. Doesn’t that sound fun?”

Tenn beams. “Yes! Tenn-nii likes -,”

His words get cut off by a series of coughs, with Riku holding him through it. Riku finds it almost funny - how their situations are now reversed and Tenn’s now depending heavily on him, both physically and emotionally. Tenn lets out a distressed whine again, hugging Riku tighter as he presses his hot cheek against Riku’s shirt.

“Tenn-nii feels icky…” Tenn complains, “Tenn-nii hates this feeling.”

“I know,” Riku says gently, “Tenn-nii wants to get better quickly, right?”

“Mm-hm.”

“Did you have your medicine yet?”

Judging by the way Tenn stills in his arms, he could tell that he hasn’t. Come to think of it, as a child, Tenn didn’t particularly like the taste of cough medicine. He put up a strong front for Riku, who hated it more than he did, but Riku remembered the pure grimace on his face when he had to take them. 

Riku doesn’t doubt that Tenn has probably grown out of that habit, but in his current state of mind, it would seem that the distaste has temporarily returned.

“Tenn-nii doesn’t want to,” Tenn mumbles.

“You won’t get better if you don’t take it, Tenn-nii,” Riku says.

Tenn shakes his head indignantly. “Tenn-nii doesn’t want to! Tenn-nii doesn’t need it.”

“It isn’t that bad, Tenn-nii,” Riku tries, “It tastes like grapes. You like grapes, right?” Carefully releasing Tenn from his hold, he reaches over to the bedside table where the small bottle of medicine and spoon already await. Tenn tenses as he watches Riku pour the dark purple liquid onto the spoon, his head shaking vehemently when Riku holds out the spoon towards him.

“Here, Tenn-nii. Only one spoon, okay?”

“No, Tenn-nii don’t wanna!”

“Just one,” Riku persuades, “See? It’s not that much. Once you take this, we can do something fun, alright?”

Tenn remains stubborn, shaking his head over and over again to the point that Riku is starting to worry that he might get a headache from it. His expression is already twisting into displeasure, his eyes shining with unshed tears.

“Medicine tastes yucky!” he screams, “Tenn-nii don’t wanna! Don’t! Wanna!”

“Tenn-nii, don’t -!”

During his apparent tantrum, Tenn had started to flail his arms, and one of them knocked out the spoon from Riku’s hand. Unable to catch it in time, the spoon spills the medicine all over Tenn’s shirt, staining the white fabric deep purple.

For a moment, there is only a stunned silence.

Then, the tears that gathered in Tenn’s eyes begin to roll down his cheeks as Tenn breaks out into another wailing sob.

“Tenn-nii made a mess!” he cries, “Now Riku will get angry!”

Riku blinks owlishly for a split second, before he quickly pulls Tenn into another embrace, making shushing sounds as he does. Tenn’s stained shirt is probably staining his own as well but right now, Riku couldn’t bring himself to care. “No, no. I’m not angry!” Riku assures, “It’s an accident. I’m not angry.”

“Riku’s only saying that...Riku is lying. Tenn-nii knows!” Tenn insists with a sob. “Tenn-nii is sorry!”

Riku’s heart softens further, his lips pulling into a tender smile as he rubs circles onto his brother’s back.

“Silly sweetheart,” Riku coos, “I’m not lying. I really am not angry. But it’s good that you apologized. You’re a good boy, Tenn-nii.”

That seems to have temporarily stopped Tenn’s tears as the boy looks up at him with watery eyes. “Riku is not angry?”

Riku shakes his head. “It’s not your fault. You’re right. Medicine tastes yucky. I don’t like it either.” He makes a disgusted expression as he sticks out his tongue, which manages to elicit a small giggle from Tenn. “But Tenn-nii, medicine makes you feel better. I take it when I’m sick too. So if you want to get better, be a good boy and eat it, okay? Just one spoon at a time.”

Tenn hesitates, before he slowly nods his head. “Okay…” His bottom lip sticks out into a pout, and god  _ dammit _ , that’s the cutest thing Riku has ever seen. 

“Okay then, Tenn-nii. Let’s eat your medicine and after that, we can have a bubble bath! You like bubble baths, right?”

The way Tenn’s face instantly lights up nearly has Riku prostrating to the heavens for allowing him to witness such an adorable look from his brother.

“Tenn-nii loves bubble baths! Can we play with Mr. Ducky?” he asks excitedly. 

Mr. Ducky is a toy duck Riku has seen sitting on Tenn’s bathtub the last time he was here. Outside of his child's headspace, Tenn had been embarrassed when Riku pointed it out, huffing and puffing as he flushed and folded his arms, avoiding giving Riku a straight answer.

“Okay,” Riku says with a laugh.

“And Mr. Beary?” Tenn presses, pointing to the stuffed bear sitting against the pillow. It had been a gift from Gaku and Ryuu during one of Tenn’s rare moments where he slips into this persona, and again, while Tenn had been shy about it, he never kept it far from him.

“Mr. Beary might get wet and you won’t be able to cuddle with him later,” Riku points out, “We can give him a bath some other time, okay?”

Tenn pouts again but nods. “‘Kay…”

Riku reaches for the medicine again, smiling when he sees Tenn sitting obediently still this time, even readily opening his mouth for Riku to feed him the medicine. Riku bites back a laugh when Tenn’s face becomes a mask of grimace when he forces himself to swallow the medicine.

“Good boy!” Riku praises when Tenn is done, “Now let’s get you out from these dirty clothes and have a bubble bath, alright?”

“Yay!” Tenn cheers, and this time, Riku allows himself to smile as widely as he could. 

He kisses Tenn’s temple, enjoying the way Tenn giggles in delight when he does, and scoops Tenn into his arms to carry him to the adjoined bathroom. Tenn lets out an excited squeal, holding onto Riku’s neck and smiling so widely that Riku’s heart soars just looking at it.

Tenn’s always such a delight to look at, but like this, when his walls crumble down and he allows himself to be vulnerable and dependent on Riku, Tenn makes Riku’s heart skip multiple beats with every reaction he gives him.

He walks into the bathroom and sets Tenn down onto the stool next to the tub, unable to resist patting his head when Tenn giggles at him.

“Let’s get these clothes off,” Riku says cheerfully.

“Tenn-nii can do it!” Tenn says, “Tenn-nii is a big boy now!”

Riku laughs. “Is that so? Okay then. You go ahead and undress while I fill the tub, okay?”

“Okay!”

Tenn keeps his word, because by the time Riku has the tub filled up with water up to his thigh, Tenn is already waiting for him as he sits on the stool, gripping the shower head. He’s undressed completely, with his clothes strewn carelessly onto the floor. 

It’s funny. Riku has seen Tenn naked countless times since they mostly grew up together and due to the...current nature of their relationship, Riku had developed... _ thoughts  _ towards the image of Tenn stripped bare for him to see.

But perhaps it’s because of the way Tenn is now looking at him with a gaze of childish trust, those thoughts didn’t appear in Riku’s head this time. Tenn looks...surprisingly pure like this, and the situation right now merely gives off the feeling of the many baths they shared while growing up. Riku chuckles and pats Tenn’s head, shaking his head fondly at the boy.

“You’re supposed to put your clothes away properly, Tenn-nii,” he chides without bite, “But I’ll forgive you this time. The water’s warm and I already mixed in the soap, so why don’t I shower you first?”

Tenn nods happily. “Okay!”

Tenn sits there obediently as Riku washes him down before he declares that it’s time for Tenn to sit in the tub. Tenn had practically screamed in joy, scrambling to get into the tub that Riku had to remind him to be careful. Still, it’s a sight to see Tenn being so unrestrainedly happy like this - to see him smile so widely as he plays with his rubber duck in the water and calling Riku over to ask him to wash his hair. It almost makes Riku forget that Tenn’s currently sick and he might have, if he didn’t feel how hot Tenn’s skin is whenever he touches him.

Again, still.

It’s nice to see Tenn so happy, even if he has to temporarily regress his mental state to allow himself to be vulnerable and honest with his emotions.

Riku unconsciously clutches a hand at his chest. It’s a bittersweet feeling when he thinks about it. Riku really is spoiled, because he has the privilege to be unrestrained with his emotions. He’s allowed to be happy when he is. He’s allowed to be angry. He’s allowed to feel insecure. Iori might scold him occasionally for wearing his heart on his sleeves, but Riku knows he genuinely cares. Even on stage, Riku’s able to be honest with himself and his fans would still love him for it.

Tenn, on the other hand, has been putting up a front perhaps his entire life. He had put up a front of a strong older brother to take care of his sickly younger one. He puts on an angelic smile to his fans to please them, and even during his time of difficulty, he never lets his strong front slip, putting on a brave smile for everyone to see. That one time he cried on stage was his only moment of weakness, and he never showed it again.

And even now, with Tenn slipping into his child persona to allow himself to be a little more vulnerable and dependent for once, Riku doesn’t pretend to overlook the fact that it’s a habit that Tenn isn’t exactly proud of. He had kept it hidden from even Riku for a long time, and if it weren’t for the fact that Riku had discovered it by accident, with Ryuu and Gaku begging him to keep it a secret, Riku would have never found out.

Although Tenn trusts him now to slip into this headspace when he’s around, it still leaves a bittersweet feeling in Riku’s chest that Tenn had to resort to this to allow himself to be honest.

“Riku…?”

The sound of his name being called snaps Riku out from his reverie. Tenn is looking at him with big eyes, strands of his hair sticking onto his forehead and around his eyes. His hand feels hot when he touches Riku on the cheek.

“Riku is okay?” he asks.

“I’m okay,” Riku says, “Sorry. I got distracted.” He flashes Tenn a warm smile. “Are you done now? You shouldn’t stay in the water for too long. You’re still sick, you know.”

“But I’m still not done playing with Mr. Ducky!”

“We can play again tomorrow morning. How’s that sound?”

“Mm...okay…”

“Good boy,” Riku answers, “Come on. Let’s get you dry and you can choose your own clothes!”

Tenn beams, and once again, Riku’s heart soars at the mere sight of it.

“Mmph!”

The outfit Tenn ends up choosing a little while later, when he’s all dried and bundled in warm towels, is a piece that even Riku himself found himself flabbergasted that Tenn even owns. It’s a soft pink frilly nightgown that is clearly at least one size too big for Tenn, as it keeps slipping off one shoulder. It, however, only reaches up to Tenn’s knees, so it reminds Riku of a strange frilly oversized shirt than a nightgown. He even reaches over for a pair of white knee socks, his face scrunched up in concentration as he pulls them up his legs.

His feet get cold at night, he explains. Well, it’s currently winter so Riku isn’t really surprised, but he still can’t get over the nightgown Tenn has, and he honestly can’t imagine him buying that himself willingly. It’s  _ cute,  _ don’t get him wrong, especially since Tenn is wearing it. But he also knows that outside his current headspace, Tenn doesn’t...he doesn’t have those kinds of preferences in clothing.

**_Oh that? That was a gift from a fan. Tenn never throws his gifts away, so I’m not surprised he brought it with him when he moved to Ryuu’s place._ **

**_It’s good that he found a use for it then._ **

Is what Gaku texts him when Riku asks. Part of him wonders if he shouldn’t have sent the picture of Tenn adorably playing with his stuffed bear as he wears the nightgown, because knowing Gaku, the man would probably tease Tenn with it one way or another.

Oh well, he’ll worry about it if he crosses that bridge. For now, he sits next to Tenn on the bed, hooking an arm around Tenn’s shoulders so the boy leans against him. He sees the way Tenn’s eyes have begun to droop, meaning the cough medicine is finally taking into effect. His grip on Mr. Beary is slackening and when Tenn turns to Riku with open arms, Riku immediately scoops into a hug and carries him like a child.

“Is Tenn-nii heavy…?” Tenn asks sleepily, holding onto Riku tight.

“Nope! Rather, I think you need to eat more, Tenn-nii. You’re as light as feathers.”

Tenn laughs a little, though he yawns immediately after. “Tenn isn’t a bird...Silly Riku. Tenn-nii doesn’t have feathers,” he mumbles drowsily.

“Is Tenn-nii sleepy now?” Riku asks with an indulgent smile.

“No,” Tenn denies, but he yawns again, instantly betraying his words, “Tenn-nii wants to play...with Riku more…”

“Shh. We can play again tomorrow when you’re a bit better, okay?”

“Mm...okay…”

“Let me sing to you, Tenn-nii.” Riku presses a kiss on Tenn’s temple. “My good boy.”

Holding Tenn tight, Riku hums a song, rocking on his heels as he does. It's reminiscent of what his mother used to do in the past, and what Tenn used to sing to him when Riku’s asthma attacks prevented him from sleeping. He sings back the song to Tenn, feeling the way Tenn’s grip on his shirt is loosening. Tenn’s breathing evens out, and by the time the song ends, Tenn is fast asleep in his arms.

Riku lays him down onto the bed, tucking him in before brushing away his hair from his eyes. Lying down next to him, Riku continues to pat his back, humming to himself as he watches Tenn sleep. Peaceful, even in the midst of a fever.

Riku doesn’t remember when, but he eventually slipped into unconsciousness, his hand resting on Tenn’s warm back.

Riku wakes up to a sound of whimpering, and something burning against his skin.

“Tenn...nii…?” he says groggily.

Something grips his sleeves.

“Riku…” he hears Tenn whimpers, his voice pained, “Riku...Tenn-nii feels hot all over.”

Fuck. Did his fever get worse? Riku scrambles for the light switch above the bed, turning on the dim bed light before turning towards Tenn. Sure enough, he sees the boy curled into himself, one hand gripping Riku’s sleeve. His forehead is dotted with cold sweat and his legs are squeezed together as he crumples forward.

“Tenn-nii?” Riku says, alarmed, “Are you in pain anywhere?! If you are, we can go to the hospital -,”

“No!” Tenn shakes his head. “No hospital! Hospital scary…” He pauses. “And...Tenn-nii…”

He bites his bottom lip, and to Riku’s surprise, Tenn is starting to look...embarrassed? 

“Tenn-nii...feels weird…” Tenn hesitates. “Down there.”

Riku furrows his eyebrows in confusion. “What do you mean, Tenn-nii? I -,”

As he says this, his eyes travel downwards automatically and almost instantly, he understands what Tenn meant. His mouth falls open into an ‘o’, his eyes widening. 

“A-ah…”

Tenn is trying to hide it by squeezing his legs together, but Riku could see it as plain as day.

Tenn is hard.

Well.

Riku’s heard of this, though he has never experienced it personally. Fevers can sometimes cause someone to be aroused, and while Riku doesn’t quite understand the science behind it, seeing Tenn’s state now makes it clear that there is nothing Riku could refute.

But as far as Riku is concerned, Tenn is still in his child persona.

Which makes this  _ incredibly  _ awkward at best. And _ incredibly _ scandalous at worst. 

While he’s so wrapped up in his thoughts, he didn’t realize Tenn had moved to kneel in front of him and grasp his shirt again, until he feels warm lips on his own and realizes too late that Tenn is now kissing him.

“Mmph-?!”

Riku’s hands fly up to grip Tenn’s arms and he forces himself to break off the kiss, looking at Tenn incredulously. “Tenn-nii?! W-what are you doing?”

It’s not the act of kissing that surprises Riku so much. They’ve kissed plenty of times before due to the nature of their relationship together - and definitely went beyond that -, but Tenn is also not in his normal headspace and for some reason, Riku feels...unsure of how to treat Tenn in terms of  _ that  _ when Tenn’s mind still that of a child’s. It feels...wrong, somehow.

Tenn, however, is pouting at him.

“Riku...Tenn-niii feels really weird down there,” he says softly, his blush indicating his embarrassment. Nevertheless, he continues to look at Riku determinedly. “And I heard kissing makes it better. Tenn-nii is a big boy now! Tenn-nii knows what kissing is.”

Yes, well. Riku doesn’t doubt that but -

“Where did you learn that, Tenn-nii?” Riku asks nervously.

“I saw it once! On TV! Ryuu is kissing a woman and he said something like…” Tenn pauses, thinking, “That he’ll make her feel good!”

Such words coming from Tenn shouldn’t be odd - Tenn is an adult, after all, and his voice and appearance still reflects that despite his current persona. But Riku finds himself screaming as he slaps a hand over Tenn’s lips either way, feeling strangely scandalized that Tenn is saying those things.

“Okay, okay!” Riku says hurriedly, “I…” He sighs heavily, hanging his head. “I honestly don’t know how to feel about this but…” He peeks at Tenn. “I guess I should help you get rid of that, either way.” He eyes the obvious hard-on in between Tenn’s legs. Tenn at the very least had the decency to look embarrassed being looked at like that, but he is leaning forward again and Riku instantly knows what he’s going to do.

“Are you sure you want this?” Riku asks again.

“Mm-hm,” Tenn nods, “It feels...weird. But it also feels…”

Even in the dim light, he could see the tip of Tenn’s ears reddening.

“It feels good,” he mumbles, “Tenn-nii sounds weird.”

Tenn-nii sounds absolutely -

Riku is kissing him again before he could finish that thought, and Tenn -

Tenn sinks into him readily, melting into the kiss as he allows his lips to be parted by Riku’s tongue. Even in this current state of mind, Tenn’s body remembers how to be around Riku. Riku really shouldn’t be surprised, yet he is anyway, and despite his earlier discomfort, Riku’s arms move in autopilot to snake around Tenn’s waist, bringing him closer towards him. He feels the flimsy material of Tenn’s nightgown, and the warmth of Tenn’s fevered body.

When he feels something rub against his groin, he breaks off the kiss to look downwards, his eyes widening when he sees Tenn grinding against him, rolling his hips towards him. The boy himself looks confused, as if he’s unsure why he’s doing what he’s doing.

“Riku…” he says breathlessly, “T-Tenn-nii doesn’t know why but...t-this feels good. W-what’s going on, Riku?”

“It’s your fever, Tenn-nii,” Riku says in a soothing voice, “It’s making you feel this. Don’t worry. I’ll...I’ll get rid of it, if you’ll let me.”

“Kissing isn’t enough?” Tenn asks.

Riku smiles a little. “I’m sure if we try it might be, but we usually handle it differently.” He pauses, searching Tenn’s face. “Tenn-nii, do you trust me?”

Tenn nods. “Tenn-nii always trusts Riku.”

Riku’s smile widens, his heart growing fond. “Okay. Tenn-nii, lean against me, okay? Relax. I’ll take care of you. And if you feel uncomfortable, just say stop, okay? I’ll stop.”

Tenn blinks once before he nods. He leans in against Riku, propping his head on Riku’s shoulder. He shudders when Riku kisses his neck as if to reassure him, his hand slipping downwards in between them.

“Hh-n!”

The way Tenn trembles against him when Riku’s hand slips under Tenn’s nightgown and into his panties to touch his cock is  _ magnificent. _

“R-Riku is touching....there…” Tenn whispers, “Isn’t it...Tenn-nii is dirty. Riku shouldn’t -!”

“Do you want me to stop?” Riku asks.

Surprisingly - or rather, unsurprisingly - Tenn shakes his head. “N-no...it feels weird but also...it feels -,” Tenn lets out a shuddering breath. “It feels  _ good _ .”

“Mm, I’m glad,” Riku murmurs, “I’m going to continue, okay? If you feel weird and want to stop, tell me, alright?”

After Tenn nods, Riku exhales, hesitating for a brief second. He’s oddly nervous - it’s not as if he’s never done this with Tenn before. Granted, they never did it when Tenn is in this state and it makes Riku want to be more careful with him than usual.

Even though he knows that gentleness is quite far from what Tenn typically wants.

Pushing that thought away, he begins rubbing his hands up and down Tenn’s cock. Slowly at first, to gauge the boy’s reactions. The boy shudders and jerks against him, but he doesn’t push Riku away or say anything to stop him. The only sounds he makes are soft whimpers, occasionally intermingling with quiet moans. It’s rather different than the ones he’s used to listen from Tenn during the other times they had sex. 

This version of Tenn seems a little unsure. Confused, even. But he doesn’t push Riku away. Instead, he holds onto him tighter, and when Riku brushes his thumb against the slit, now wet with pre-cum, Tenn gasps loudly, his fingers digging into Riku’s shoulder.

“Did that feel good?” Riku asks.

Tenn nods. “M-mh-hm…” Tenn’s breathing is loud in Riku’s ear. “It feels...something sharp going up Tenn-nii’s body. But Tenn-nii l-likes it.”

Riku takes this as a sign to continue, his hand continuing stroking Tenn’s hard length and relishing every reaction Tenn gives him. By the time he increases the intensity of his movements, Tenn is gasping and writhing against him, his moans now increasing in volume. 

He doesn’t push Riku away once. 

“R-Riku,” Tenn gasps, “T-Tenn-nii feels -,”

“Are you going to come, Tenn-nii?” Riku asks, sounding a little breathless himself. Tenn’s sweet sounds send heat down to his groin, and Riku finds himself getting harder by the second. Apparently, he’s not the only one who noticed.

He lets out a little yelp of surprise when Tenn suddenly pulls him down onto the mattress, causing Riku to topple on top of him when Tenn lies back down on the bed. His hands brace themselves at Tenn’s sides before he crashes fully onto him.

“Tenn-nii?”

“Riku…” Tenn whispers, “Tenn-nii wants to help Riku too.”

“Huh? Oh -,”

He hisses when Tenn’s hand reaches out to palm in front of Riku’s pants, feeling the shape of his hard cock in his hand. Tenn looks a little shy when he does this, but he doesn’t pull away, even looking determined to apparently return the favor.

“A-ah, you don’t need to,” Riku says a little nervously, “I will be fine.”

Tenn, however, is adamant. “Tenn-nii wants to help too. Tenn-nii is a big boy now. Tenn-nii can learn these things too, right?”

“T-Things?”

Tenn chews his bottom lip again. “A-adult things...like the things Ryuu does on TV.”

One of these days, Riku will  _ murder _ Gaku and Ryuu for allowing Tenn to watch  _ those _ things on TV when he’s in this state. 

Riku swallows. “Tenn-nii...do you know what you’re talking about?”

Riku isn’t sure if it’s the fever, but Tenn’s flushing harder now, nodding. “R-Riku c-can put this,” he says, his fingers lightly curving around the shape of Riku’s cock through his pants, “I-into…” Tenn licks his lip. “Into Tenn-nii’s hole.”

Oh god  _ almighty _ , Riku feels so fucking  _ sinful  _ right now. He thinks any second now, the FBI would come bursting through his door to arrest him, despite the fact that Tenn is a full-fledged adult. 

“Tenn-nii…” Riku’s voice is strained. “You don’t have to -,”

“Tenn-nii wants it,” Tenn insists, “If it’s Riku...Tenn-nii wants it.”

Riku lets out a shaky breath.

“I…” He chooses his words carefully. “If Tenn-nii wants it, then...let’s take it slow, okay? Tenn-nii is sick, after all. I don’t want to strain your body.” He stops to look at Tenn properly. “Tenn-nii trusts me?”

“Always,” Tenn replies earnestly.

For a split second, Riku thinks Tenn had returned back to his normal state of mind. But somehow, he knows deep inside that that’s not the case.

“Okay,” he says, his voice barely above a whisper, “Okay.” He exhales again. “I’m gonna take your panties off, alright? You’re alright with that, Tenn-nii?”

Despite his red cheeks, Tenn nods. He parts his legs, allowing Riku to slide the panties right off. Riku swallows heavily when he realizes just how damp the undergarment is with Tenn’s pre-cum. He runs his hand across Tenn’s stomach, enjoying the way the boy shudders at his touch. He lifts the nightgown up to Tenn’s chest, revealing Tenn’s cock, now flushed and leaking against the boy’s stomach. 

It makes Riku’s throat go dry just looking at it.

He shimmies his own pants down to his knees, and frees his cock from his boxers. He smirks internally when he catches Tenn looking at it, taking in the widening of his eyes and the bop in his throat as he swallows.

He positions his cock in between Tenn’s legs, before he pushes Tenn’s knees together, squeezing Riku’s cock in between the boy’s thighs. 

“Keep your legs closed, Tenn-nii,” he instructs, “I’m not gonna put it in you, yet. I don’t want to strain you.”

Tenn shakily nods his head and Riku takes that as a sign to start moving.

Riku thrusts his cock in and out from between Tenn’s thighs, making sure their cocks touch with each thrust. He bites back a hiss when they first brush against one another, while Tenn lets out another startled gasp at the sensation. It doesn’t take long until Riku begins to pick up the pace, encouraged by the sounds Tenn makes, evident of his pleasure. 

The sensation of their cocks brushing against each other is  _ amazing  _ and Riku couldn’t get enough. His movements become more and more frantic as he loses his steady rhythm. The sounds of broken moans and groans fill the room, and just as Riku could feel his release nearing, there are fists pounding lightly on his chest.

“Not enough,” Tenn says in a high-pitched keening voice, “Tenn-nii wants more.” He hits Riku’s chest with his fists again, his actions making it seem like he’s sulking. “Riku doesn’t need to be careful with Tenn-nii. Tenn-nii is a -,”

“- big boy now, I know,” Riku whispers, “I know you are, Tenn-nii. Trust me when I say this, but you look so beautiful right now that I really want to ravish you so badly, Tenn-nii.”

Tenn blushes prettily at this, as if he knows the full implication of Riku’s words.

“Then, d-do it,” he stammers, “Tenn-nii wants it.” His gaze flicks briefly towards Riku’s cock. “Tenn-nii wants this in Tenn-nii’s h-hole.”

Hearing those words from him, it’s a struggle for Riku to maintain his self-control. If it weren’t for the fact that Tenn is currently in his child’s headspace, he would have flipped Tenn over and fuck him senseless into the mattress until all Tenn could do is just to scream out his name.

Instead, he focuses himself to breathe out deeply before he eventually nods.

“It’s going to hurt if I don’t prepare you, so let me do that first,” he says, “Lean against the pillows and part your legs for me, Tenn-nii.”

As Tenn does this, Riku reaches over to open the bedside drawer where he knows Tenn keeps the lube. He uncaps the bottle and pours a generous amount onto his fingers before he returns to kneel in front of Tenn. Tenn already has his legs parted for him, and the sight of Tenn’s puckered hole just exposed to him like this -

“Remember what I told you before?” Riku asks softly, trailing his fingers around the ring of muscles, smiling when Tenn hisses at the contact.

“Tenn-nii will tell Riku to stop if Tenn-nii wants to stop,” Tenn answers.

“Good boy,” Riku praises, “You’re such a smart boy.” He leans in until their noises are touching. “I love you, Tenn-nii.”

Tenn smiles  _ brilliantly _ at him. “Tenn-nii loves Riku too.”

Riku captures Tenn’s lips into a heated kiss, and the moment he feels Tenn relax against him, he slowly inserts the first finger inside, pushing past the tight ring of muscles and into the wet heat. Tenn gasps into the kiss and stills, and Riku waits until he relaxes again before he speaks.

“Okay?”

Tenn lets out a shaky breath. “Okay.”

Riku moves his finger, pumping it in and out of Tenn’s hole at a slow pace, before he gradually begins to increase it when he can tell Tenn is beginning to adjust to the sensation. The boy gasps again when Riku adds a second finger, but he adjusts much faster this time, and by the time Riku crooks his fingers inside, brushing against that spot he knows Tenn feels the most, Tenn lets out the most beautiful cry he has ever heard. He shudders against Riku, breaking off the kiss to lean his head against Riku’s shoulder as Riku begins to finger him in earnest.

It’s a reminiscence of their first time - with Riku taking things slow with Tenn and them learning from each other’s reactions before fumbling their way through the entire process. Although none of them are inexperienced at this point, Tenn might as well be when he’s like this, like he’s re-learning how pleasurable sex could feel once he gets to know his body better.

Tenn’s sighs and moans are sweet in his ear. Riku adds a third finger, scissoring them inside Tenn’s hole, feeling the muscles eventually loosening. At the same time, Tenn is grinding against him again, no doubt eager for some friction. Although his mind might not remember the times he’s done this with Riku in the past, his body certainly does.

Which is why -

“Tenn-nii wants it now,” Tenn gasps, “R-Riku, please give it to Tenn-nii. Tenn-nii wants it so much.”

“Alright, Tenn-nii,” Riku answers, “You’ll be a good boy and lie back against the pillows for me, won’t you?”

“Tenn-nii will. Tenn-nii is Riku’s good boy.”

Riku smiles. “Yes, you are.”

Once Tenn lies back against the pillows, his hands placed at each side of his head, Riku parts his legs further and positions his cock against Tenn’s waiting hole. He catches Tenn’s eyes, flashing him a reassuring smile.

“Tell me if it hurts,” he says.

“Mhm.”

He could tell that Tenn is nervous. In his current state, this might as well be Tenn’s first time. He’s doing adult things with his beloved Riku, and while the idea is extremely scandalous, it is  _ thrilling _ all the same.

Riku’s not surprised when Tenn immediately tenses when Riku starts to push in. He takes his time, starting from the tip and all the way down his length. By the time he’s fully up to the hilt, Tenn is trembling underneath him, tears pricking the corner of his eyes.

Despite this, when he looks at Riku, Riku could see the trust in his eyes. The boy even flashes Riku a watery smile, as if to reassure him.

“I-it hurts a little,” Tenn admits, “B-But, Tenn-nii is okay. R-Riku can continue.”

“You sure?”

“Uh-huh,” Tenn says, “Tenn-nii trusts Riku, Tenn-nii loves Riku. So it’s okay.”

Riku leans forward to kiss the tip of Tenn’s nose.

“As I love you, Tenn-nii,” he murmurs.

He waits for a few seconds more until he’s sure Tenn adjusts a little better, before he begins to move.

God, being inside of him like this - it’s definitely different than just thrusting in between his thighs or fingering him.

“Mhn~!” Tenn moans, “R-Riku, Tenn-nii feels...weird…!”

“Hm? What do you mean, sweetheart?” Riku asks breathlessly, focusing on the way Tenn’s tight heat is sucking him in. It’s exactly how he remembers it - he’s reminded of why he couldn’t get enough of Tenn. Couldn’t get enough of his own twin brother.

“Tenn-nii’s insides...feel funny…! Like...they’re moving on their own…” Tenn lets out another moan when Riku thrusts in a little deeper into him. “Tenn-nii feels hot all over! R-Riku, is Tenn-nii okay? Tenn-nii feels a little strange - hnn~!” His legs curl around Riku’s waist as he throws his head back, clearly overwhelmed by the sensation of Riku’s cock inside of him.

“Do you feel good too, darling?” Riku asks, his voice hoarse, “Do you feel good when I thrust into you like this?”

Tears roll down Tenn’s cheeks as he nods. “Mh-hm! Tenn-nii feels really good! R-Riku, give Tenn-nii more! It feels strange but so good~!” He lets out a breathless giggle. “Is this what adult things feel like? H-ah, Tenn-nii wants more!”

Riku leans forward to kiss Tenn’s throat, his feverish skin now slicked with sweat. “I’ll make you feel good, darling. My baby boy. My good boy, I’ll make you feel absolutely  _ amazing _ .”

He finds a primal satisfaction in the way Tenn cries out when he enunciates the last word with another hard thrust. He picks up his pace, indulging himself in the way Tenn cries and moans and gasps, while Riku’s cock continues to be sucked into Tenn’s wet heat. The sounds of skin slapping against skin and broken moans filling the room are absolutely  _ obscene  _ and Riku loves every second of it.

The rough material of Tenn’s socks brush against his sides as Tenn curls his legs tighter around him, and his nightgown has ridden up until the material rests against his nipples, now red and upright against his chest. Riku, unable to help himself, takes one into his mouth, licking the tip with his tongue.

“Hya~!” Tenn squeals, “R-Riku, that feels -!” He lets out another high-pitched moan when Riku lightly bites the nipple in between his teeth, all the while thrusting into Tenn with fervor. 

Hands tangle in Riku’s hair, pulling the locks rather roughly.

“Tenn-nii...feels...hngh~! R-Riku…” he sobs, “Tenn-nii feels like he’s going to -!”

“I know, baby,” Riku says with a groan, “Let’s do it together, okay?” His hand wraps around Tenn’s cock again before rubbing it, eager to bring Tenn to a finish. “Come on, you can do it. Gh -!”

“Riku!” Tenn screams, his back arching off the mattress before he finally comes, his release spurting out in stripes. They splatter onto his stomach and his nose and cheeks, and he’s still moaning as he rides his orgasm. At the same time, Riku comes with a deep groan, releasing deep inside Tenn.

Riku collapses beside Tenn after his orgasm wears off, taking time to catch his breath. Beside him, Tenn has started to curl beside him, his hand reaching for Riku again. When Riku finally turns to Tenn, he finds the boy’s eyes already fluttering close. Tenn’s lips part into a soft yawn.

Riku smiles tenderly at him, pulling Tenn close. “Feeling sleepy, sweetheart?” he crooned, “You can rest now. You did so well. I love you, Tenn-nii.”

Tenn, his eyes already closed, gives him a sleepy smile.

“Mm...Tenn-nii loves Riku...too…”

As Tenn drifts into sleep, Riku holds him close, patting his back gently until he too, eventually drifts back into unconsciousness. 

“Good morning, Riku.”

“Mm…? Tenn-nii?”

Tenn is smiling down at him, propping his chin on his hands as he looks at him. “Thank you for staying with me last night. I’m feeling much better now.”

Tenn is no longer calling himself by his name. Which means -

“I’m glad,” Riku says instead, reaching out to stroke Tenn’s cheek, “But it’s still our day off. So come lie beside me for a little while longer.”

Tenn laughs. “I’ll indulge you for today.”

Riku returns the laughter with a tender smile. “You indulge me every day.”

Tenn lies beside him on the bed, draping his arm across his chest. He snuggles up to Riku, and soon, Riku could hear a soft crooning of the same song he had sung to Tenn last night. Smiling to himself, Riku tucks Tenn closer to his side, resting his head on the boy’s hair.

“I love you, Tenn-nii.”

Tenn tightens his hold on Riku.

“As I love you, Riku.”

**Author's Note:**

> u w u


End file.
